In a carburetor-type internal combustion engine, the so-called "dieseling" is a phenomenon wherein the engine continues to rotate after the ignition switch is opened due to the compression ignition of the fuel which is issued from the slow fuel supply passageway of the carburetor. In such an engine, "dieseling" is generated under a condition wherein the temperature of the intake air is relatively high.
The "dieseling" phenomonen is apt to be generated if the automobile is provided with an air conditioner, because such an engine has a so-called "idle-up device" which operates to increase the opening of the throttle valve when the throttle valve is in its idle position.